This invention relates generally to the percutaneous placement of catheters into body vessels and more particularly to a method and apparatus for simple aseptic percutaneous placement of extremely flexible, thin-walled, closed-ended catheters.
Flexible and resilient intravascular catheters have in the past been inserted and used for a wide variety of medical purposes. For example, catheters have been used for intravenous volume support, for intravenous nutrition including hyperalimentation, for administration of therapeutic fluids and drugs, and for repeated withdrawal of body fluids for laboratory analysis.
Various methods have been utilized to insert such catheters into body vessels. With respect to such insertion methods the term "distal end" refers to the rearward end of the catheter, needle, or other member which is normally situated externally of the patient's body. The term "proximal end" refers to the forward end of the catheter, needle, or other member which is inserted into the patient's body or which is disposed closer to the body than the distal end.
Flexible and resilient catheters may be surgically placed in an appropriate body vessel by exposing the vessel, incising the vessel wall, and inserting the catheter through the surgical incision. This method is less desirable than other alternatives because of the time and expertise required, the patient discomfort, and the risk of infection.
A more common technique of inserting catheters into body vessels utilizes a stiff but thin walled catheter which fits snugly over a hollow beveled needle such that the needle acts both to penetrate the epidermis and subjacent body vessel and as a guide and stiffener over which the catheter is advanced into the vessel. This method of catheter placement, although widely utilized, has several disadvantages. For one, the catheter material must have a significant degree of stiffness so that it can be advanced easily past the proximal end of the internal needle and into the vessel without bending or intussuscepting. This degree of stiffness does not allow the catheter to conform easily to curves and bends of the vessel thus causing possible damage to the vessel wall, and even vessel perforation, during catheter advancement. After insertion irritation of the vessel lining by the stiff catheter may result in inflammation and blood clot formation.
Such stiff catheter material has decreased elastic memory and thus tends irreversibly to kink upon sharp or repeated bending, resulting in catheter obstruction and failure. The tendency to kink prevents the use of this catheter type across joint spaces and other anatomic locations in which repeated flexion and extension motions are expected unless additional precautions are taken such as joint splinting or immobilization of the anatomic area of catheter insertion.
Another disadvantage of this "over-the-needle" method of catheter insertion is that the external surface of the catheter is in direct contact with the surrounding epidermis throughout the insertion procedure and thus as the catheter is advanced into the vessel it may carry epidermal bacteria into the subcutaneous tissue and possibly the vessel which may then cause tissue and vessel infection. After insertion the stiff catheter has a tendency to slide in and out of the epidermal insertion site during voluntary or involuntary motion of the tissue through which the catheter is inserted, thus leading to the likely continued intermittent introduction of epidermal bacteria into the subcutaneous tissue space.
Yet a further disadvantage of the "over-the-needle" approach is that the catheter must of necessity be open ended. This allows retrograde blood flow into the open proximal end of the catheter which may result in clot formation within the catheter lumen with subsequent catheter failure, requires continuous flow of fluid through the catheter or repeated catheter flushing to prevent such clot formation, and also allows the possibility of hermorrhage through the open ended catheter should the distal end become loosened or disconnected.
Another method of catheter insertion uses a hollow metal needle to penetrate the epidermis and subjacent body vessel; through the lumen of such introducing needle the catheter is inserted and advanced. Such catheters must be relatively stiff to allow facile advancement of the catheter through the introducing needle and into the vessel. As such they suffer the disadvantages previously described for relatively stiff intravascular catheters. Said catheters are not, however, required to be open-ended. Because the catheter is generally advanced manually through the introducing metal needle, it is free to move both forward and backward within said needle thus allowing, either inadvertently or purposefully, retrograde catheter motion across the sharp introducing needle bevel causing possible catheter nicking or shearing. The result may be damage to the catheter wall or complete shearing off of the catheter end with such piece passing centrally in the vascular system and causing serious medical consequences.
Because an appropriate female fluid flow adaptor to allow connection to a fluid source is conventionally positioned on the distal end of the catheter, the introducing needle must frequently remain proximal to the adaptor, around the catheter, and remain on the patient with a protective device such that the sharp needle is prevented from cutting or shearing the catheter with adverse results. Alternatively, the introducing needle may be of a type such as shown in U.S. Pat. No. 3,598,118 which can be split lengthwise and removed from around the catheter. A variation of this technique which does not require a splittable needle is described in U.S. Pat. No. 4,068,659 to Moorehead. In this method the fluid flow adaptor is applied to the catheter subsequent to catheter insertion and removal of the inserting needle.
Yet another method of catheter placement requires inserting a hollow metal needle into a body vessel, introducing a stiff guidewire through said needle into a body vessel, removing the needle, and threading the catheter over the guidewire percutaneously into the body vessel to a desired distance. After catheter placement the guidewire is removed. This method requires a catheter which is both open-ended and relatively rigid, thus having the associated potential problems and complications previously enumerated. In addition, the insertion technique is not completely sterile in that the external surface of the catheter is drawn through the epidermis thus causing epidermal bacteria and organisms to be drawn into the subcutaneous tissue and possibly into the body vessel by the outer wall of the catheter. In our U.S. Pat. No. 4,327,722, we describe a method of inserting a soft, flexible closed-ended catheter wherein a stiffener in the form of a stainless steel wire is inserted in the catheter and pushed to cause the catheter to be drawn into the vein.
It is thus an object of the present invention to provide an improved method and apparatus for percutaneous placement of a closed-ended catheter fabricated of extremely flexible, biocompatible material such as thin-walled silicon rubber or similar material.
It is yet another object of the present invention to provide a method of percutaneously inserting a catheter in a completely sterile fashion without the possibility of catheter contamination by operator handling or by the skin through which the catheter must pass.
Another object is to provide a placement procedure in which the operator can test the position of the inserting needle within the body vessel as the catheter is being advanced into said vessel. He can thus verify that the introducing needle and the catheter are continuously disposed in the body vessel and have not become dislodged.
It is also an object to provide a method and apparatus for placing an infusion catheter in which sterile injection fluid, i.e., liquid can be infused through the catheter and into the body vessel during catheter placement. Such fluid injection will tend to dilate and expand the vessel into which the catheter is being advanced and thus facilitate catheter placement. Such fluid injection should, of course, avoid the possibility of introducing air into the bloodstream which could result in air embolism with adverse medical consequences.
It is also desirable that the method and apparatus of placing the catheter be usable in both peripheral and central venous applications. Yet another object of the invention is to provide a method and apparatus for percutaneously placing an infusion catheter which permits rapid insertion of the catheter to facilitate emergency usage, yet which results in minimum catheter trauma to the wall of the body vessel into which the catheter is being advanced. Such method and apparatus desirably dilate the blood vessel to ease advancement of the catheter therethrough.